Cellular radiotelephone system base transceiver stations (BTSs), at least for some United States (U.S.) and European Union (EU) applications, may be constrained to a maximum allowable effective isotropically radiated power (EIRP) of 1640 watts. EIRP, as a measure of system performance, is a function at least of transmitter power and antenna gain. As a consequence of restrictions on cellular BTS EIRP, U.S., EU, and other cellular system designers employ large numbers of BTSs in order to provide adequate quality of service to their customers. Further limitations on cells include the number of customers to be served within a cell, which can make cell size a function of population density.
One known antenna installation has an antenna gain of 17.5 dBi, a feeder line loss of 3 dB (1.25″ line, 200 ft mast) and a BTS noise factor of 3.5 dB, such that the Ga−NFsys=17.5−3.5−3.0=11 dBi (in uplink). Downlink transmitter power is typically 50 W. With feeder lines, duplex filter and jumper cables totaling −3.5 dB, the Pa input power to antenna is typically 16 W, such that the EIRP is 16 W+17.5 dB=1,000 W.
In many implementations, each BTS is disposed near the center of a cell, variously referred to in the art by terms such as macrocell, in view of the use of still smaller cells (microcells, nanocells, picocells, etc.) for specialized purposes such as in-building or in-aircraft services. Typical cells, such as those for city population density, have radii of less than 3 miles (5 kilometers). In addition to EIRP constraints, BTS antenna tower height is typically governed by various local or regional zoning restrictions. Consequently, cellular communication providers in many parts of the world implement very similar systems.
Restrictions on cellular BTS EIRP and antenna tower height vary within each country. Not only is the global demand for mobile cellular communications growing at a fast pace, but there are literally billions of people, in technologically-developing countries such as India, China, etc., that currently do not have access to cellular services despite their willingness and ability to pay for good and inexpensive service. In some countries, government subsidies are currently facilitating buildout, but minimization of the cost and time for such subsidized buildout is nonetheless desirable. In these situations, the problem that has yet to be solved by conventional cellular network operators is how to decrease capital costs associated with cellular infrastructure deployment, while at the same time lowering operational expenses, particularly for regions with low income levels and/or low population densities. An innovative solution which significantly reduces the number of conventional BTS site-equivalents, while reducing operating expenses, is needed.